Although prescription drugs offer tremendous health benefits, significant improvement in our system of prescribing will be required before these benefits can be achieved. Electronic prescribing (e-prescribing) represents an important means of promoting better prescribing, through both increased efficiency in the prescribing process and better outcomes of medical therapy. Understanding whether e-prescribing systems can effect the desired changes requires detailed study of the prescribing system, from the prescriber encounter with the patient through the process of electronic prescribing and on to the clinical outcomes experienced by patients. Our proposed research will evaluate the full spectrum of e-prescribing. We have an active partnership with the makers of an office-based e-prescribing system that is already in widespread use and with multiple insurance companies and public programs who will provide claims data. The proposed research will proceed in three phases. In the first phase, we will use data from the e-prescribing system to evaluate physician responses to decision support interventions and alerts. For the second phase, we will bring together experts on information technology and experienced survey researchers to develop a qualitative study demonstrating the impact of e-prescribing on prescribing processes and outpatient workflow, including a large-scale survey to develop a detailed understanding of how e-prescribing can be integrated into medical practice. The third phase of the research will draw on decades of experience studying large medical databases to evaluate prescribing decisions and clinical outcomes when e-prescribing is initiated. We will link the e-prescriptions issued to patients with the pharmacy claims for those patients and will generate a comprehensive dataset to evaluate the true clinical impact of e-prescribing. Although the public interest in e-prescribing is growing, including recent proposals to provide eprescribing systems to all physicians, the data on how e-prescribing systems are used and what impact they actually have on prescribing processes and outcomes are still quite limited. The findings of this research will provide important lessons for clinicians, researchers, insurers, policy-makers, patients, and all those with an interest in improving the use of prescription drugs.